World first: Scientists extract electricity from heat in a very unusual way

Scientists Make Breakthrough in Power Generation — Marking First Demonstration of Transverse Thermoelectric Conversion

Researchers at Tokyo University of Life Sciences have demonstrated transverse thermoelectric conversion in WSi2, paving the way for more efficient thermoelectric devices. Interesting Engineering reports on this.

The study involved conducting experimental and computational studies of the transport properties of single crystals of WSi2, also known as tungsten disilicide.

The researchers analyzed the properties of the single crystals using a combination of physical experiments and computer simulations. They measured the thermoelectric power, electrical resistance, and thermal conductivity of a single WSi2 crystal along its two crystallographic axes at low temperatures.

The findings showed that the axis-dependent polarity of the conductivity of WSi2 stems from its unique electronic structure, characterized by mixed-dimensional Fermi surfaces.

This structure shows that electrons and holes (positive charge carriers) exist in different dimensions. The Fermi surface — it is a theoretical geometric surface that separates occupied and unoccupied electronic states of charge carriers within a solid material.

In WSi2, electrons form quasi-one-dimensional Fermi surfaces, and holes form quasi-two-dimensional Fermi surfaces. These unique Fermi surfaces create direction-dependent conductivity, which enables the TTE effect.

To demonstrate the transverse thermoelectric effect, the researchers applied a temperature gradient at a 45-degree angle to the crystallographic axis.

The researchers observed strongly sample-dependent transport properties, which were also observed in previous studies, and together with first-principles calculations, they show that such sample-dependent transport properties arise from zone-dependent carrier scattering rates.

The calculated zone-allowed conductivity shows that the mixed-dimensional electronic structure, consisting of a quasi-one-dimensional electron Fermi surface and a quasi-two-dimensional hole surface, is the key property for the axis-dependent polarity of the conductivity, according to with the study.

In the study, the scientists noted that they observed differences in how these charge carriers conduct electricity from sample to sample, consistent with previous research.

Using first-principles modeling, the researchers showed that these changes were caused by differences in how charge carriers diffuse through imperfections in the WSi2 crystal lattice structure.